Computer Hardware User's Guide

Delayed Branches

7-10

Example 7–6. Incorrectly Placed Delayed Branches

B1: BD L1

NOP

B2: B L2 ; This branch is incorrectly placed.

NOP

For faster execution, it might still be advantageous to use a delayed branch

followed by NOP instructions by trading increased program size for faster

speed. This is shown in Example 7–7 where a NOP takes the place of the third

unused instruction after the delayed branch.

Example 7–7. Delayed Branch Execution

* TITLE DELAYED BRANCH EXECUTION

LDF* +AR1(5),R2 ; Load contents of memory to R2

BGED SKIP ; If loaded number >=0, branch

; (delayed)

LDFN R2,R1 ; If loaded number <0, load it to R1

SUBF 3.0,R1 ; Subtract 3 from R1

NOP ; Dummy operation to complete delayed

; branch

MPYF 1.5,R1 ; Continue here if loaded number <0

SKIP LDF R1,R3 ; Continue here if loaded number >=0